Needle thread takeup mechanisms for sewing machines

ABSTRACT

A needle thread takeup for a sewing machine comprising mechanism for imparting motion to the thread eyelet extremity of a takeup lever in a nonplanar closed loop path.

United States Patent Inventor Ralph E. Johmon Boonton, NJ Appl. No. 856,722 Filed Sept. 10, 1969 Patented Feb. 9, 1971 Assignee The Singer Company New York, N.Y. a corporation of New Jersey NEEDLE THREAD TAKEUP MECHANISMS FOR SEWING MACHINES 8 Claims, 9 Drawing Figs.

Int. CL

Field of Search 112/248, 241, 59, 97, 172

[56] References Cited UNITED STATES PATENTS 690,004 12/1901 Ammerman 1 12/245 1,065,058 6/1913 Lenler l12/172X 1,740,380 12/ 1929 Stephenson 1 12/248 Primary ExaminerPatrick D. Lawson Assistant Examiner-George H. Krizmanich Attorneys-Marshall J. Breen, Chester A. Williams, Jr. and

Robert E. Smith ABSTRACT: A needle thread takeup for a sewing machine comprising mechanism for imparting motion to the thread eyelet extremity of a takeup lever in a nonplanar closed loop path.

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ATT RNEY BACKGROUND OF THE INVENTION This invention relates to a needle thread takeup mechanism for sewing machines,- and more particularly, to a device including a kinematic arrangement providing highly desirable thread handling characteristics commensurate with a minimum of vibration.

The salient stages in each cycle of stitch formation which a needle thread takeup mechanism must satisfy are; payout of thread for needle penetration of the work fabric, control of the thread to accomplish formation of a needle thread loop for seizure by a movable loop taking hook or shuttle, fast payout of thread for concatenation of the needle thread about the under or bobbin thread holding means, and takeup of the thread from the loop taker and into the work in which the stitch is to be set. In order to accommodate each of these stages, the needle thread must be controllably slackened, expanded and drawn tight at various times thus requiring the handling of a substantial length of thread notwithstanding that only a minimal thread length is digested in the formation of a single stitch.

Conventional link takeups have an oscillatory or reciprocatory lever including a needle thread eyelet extremity are advantageous at low speeds since they have been developed to closely match the thread requirements of the stitch forming instrumentalities. n the other hand, at high speeds the link takeups are inherently troublesome due to excessive vibration.

Rotary takeups obviate undesirable vibration but present serious problems in the provision of adequately precise control of the needle thread in accordance with the critical demands of the loop taker. Rotary takeups heretofore known, moreover, provide relatively extensive thread engaging surfaces which compound the complexity of design and increase the problem of abrasion of the thread.

SUMMARY OF THE INVENTION It is, therefore, the object of this invention to provide a takeup device having a single thread engaging eyelet which continuously and positively controls the needle thread during each and every stage of thread takeup and thread slackening.

It is a further object of this invention to provide a means for precisely controlling the needle thread in accordance with the thread requirements of the stitch forming instrumentalities at all speeds and particularly at extremely high speeds common in the industrial environment.

The present invention, as will hereinafter be described, includes input means generating a cone in space for driving the eyelet extremity of a takeup member in a nonplanar closed loop path, which path is particularlyadvantageous and suitable for the accommodation of displacement characteristics of needle thread takeup action.

DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in I view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in theaccompanying drawings of a preferred embodiment in which:

FIG. 1 represents an end elevational view of a sewing machine illustrating the present invention with the parts in positions corresponding to the top dead center position of the needle bar;

FIG. 2 represents a vertical cross-sectional view of the sewing machine with the parts positioned as in FIG. 1;

FIG. 3 represents a horizontal cross-sectional view of the sewing machine illustrating the takeup mechanism of the present invention taken substantially along line 3-3 of FIG. 1;

FIG. 4 represents the locus pattern of the nonplanar closed loop path traversed by the thread eyelet of the takeup mechanism of this invention including traces-of the centerline of the takeup lever at periodic intervals during a cycle of movement and the locus pattern of the takeup driving crank;

FIG. 5 represents a graph illustrating the thread demand of the stitch forming instrumentalities as compared with the thread control attained by the present invention;

FIG. 6 represents an end elevational view of the sewing head illustrating the present invention having its takeup arm in a position as the needle bar approaches bottom dead center position;

FIG. 7 represents an end elevational view of the sewing head illustrating the present invention having its takeup arm in the position of needle loop seizure by the loop taker;

FIG. 8 represents an end elevational view of the sewing head illustrating the present invention having its takeup arm in the position in which the needle thread will be castoff from the loop taker; and

FIG. 9 represents an end elevational view of the swing head illustrating the present invention having its takeup arm in stitch setting position.

DETAILED DESCRIPTION OF THE INVENTION The present invention, as shown in the drawings, is illustratedas embodied in a conventional lockstitch sewing machine having a frame including a work supporting bed 11, over which is supported a bracket arm (hot shown) terminating in a sewing head 13. Supported for endwise reciprocation in the sewing head 13 is a needle bar 15 having at its lower end a conventional needle clamp 17 in which is detachably secured a needle 19. Shiftably supported for vertical movement in the sewing head 13 is a spring depressed presser bar 21 carrying at its lower end a presser foot 23. In the bed 11 and cooperating with the needle 19 to form stitches is a conventional loop taker 25.

.loumaled in the bracket arm and extending into the sewing I head 13 as shown in FIG. 2 is an arrnshaft 27 to which a counterbalance 29 is fixed. A crank pin 31 secured in the counterbalance 29 is embraced by a driving link 33 which is pivotally connected at its opposite extremity to a stud 35 secured on the needle bar 15. Fast on the crank pin 31 at the opposite side of the driving link 33 from the counterbalance 29 is a web 37 which supports a stud 39 substantially coaxial with the armshaft 27. Secured to the stud 39 by means of a setscrew 43 is a collar 45 by which a crank disc 46 is carried for rotation on the stud 39.

As best shown in FIG. 3 the disc 46 is formed with projection 49 extending outwardly of the sewing head 13 and formed with a bearing socket 50 which is inclined relatively to the axis of the armshaft 27 and is formed with a semispherical base. The bearing socket 50 serves to drive onearm 51 of a bellcrank takeup lever 53. To this end the arm 51 is formed with an annular flange 55 from which extends a cylindrical pin 56 freely slidable in a cap 57 formed with a semispherical surface 59. An annularspring washer 63 interposed between the flange 55 and the cap 57 maintains the semispherical surface 59 of the cap 57 situated in the bearing socket 50.

Secured to the sewing head 13 by means of setscrews 62 is a face plate 64 accurately positioned thereon by two locking pins 66,66 adapted to coact with two locating recesses 68--69 formed in the head 13. The face plate 64 is formed with a circular opening 47 through which the takeup driving disc 46 extends. A block 65 is afiixed to the face plate by means of two fastening screws 70 and a bushing 67 which is secured in the block 65 by means of a setscrew 69, provides a rotatable support on an axis of the shaft perpendicular to the axis 27 for a holding member 71 which provides a universal pivotal connection for the bellcrank takeup lever 53 with respect to the sewing machine frame. The holding member 71 includes at one extremity a cylindrical stud 73 journaled in the bushing 67 and retained therein by an annular collar 75 secured to the cylindrical extremity 73 by means of a setscrew 77. The other extremity of the holding member 71 includes a clevis 79 having two limbs 81-81 between which extends a pin 83 perpendicular to the cylindrical extremity 73. The bellcrank takeup lever 53 is formed with a bore 84 in which the pin 83 is accommodated and secured in position by a setscrew 85.

The free extremity of the takeup lever arm 87 is formed with a thread eyelet 89. The needle thread which the thread eyelet 89 manipulates is directed from a source of supply (not shown) first to a conventional thread tensioning device 91 and to a check spring 93 associated therewith, and next to a thread guiding loop 97 of a wire thread guide 95 which is secured on the face plate 64. The thread is directed from the thread guiding loop 97 to the takeup eyelet 89 and to an eyelet 98 formed in the wire thread guide 95 closely adjacent to the thread guiding loop 97. The thread then is directed to a thread guide 99 on a needle bar bushing 100 and then to the needle. The kinematics of the driving apparatus of the present invention and the particular path transversed by the takeup eyelet 89 permits the utilization of the closely spaced needle thread guiding means 97 and 98 directing the thread to and from the takeup. These thread guiding surfaces being closely spaced minimize the length of needle thread which must be manipulated by the takeup in order to accommodate the thread demand of the stitch forming instrumentalities of the sewing machine.

Referring to FIG. 4, the path of motion of the takeup lever 53 and of the takeup eyelet 89 thereof is illustrated. The takeup lever arm 51, which may be termed the input means describes a conical path in space. Since the semispherical surface 59 of the cap 57 moves circularly, the conical path described by the takeup arm will be right circular when the inte rsecting axes of the universal pivotal connections defined by the holding member 71 is disposed along the axis of the armshaft 27. By adjusting the bushing 67 in the block 65 the apex of the conical path may be shifted so that the input means will describe an oblique conical path. The slidable cap 57 on the lever arm 51 will accommodate such an oblique conical path or motion.

The takeup lever arms 87 and 51 are joinedat an angle A as indicated in FIG. 3, so that the takeup eyelet 89 will be disposed laterally opposite from the conical path of the lever arm 51 and also laterally opposite from the continuation of the traces of the conical path of the takeup lever am 51 on the opposite side of the universal pivotal connection provided by holding member 71. In the form illustrated in the drawings, the angle A is 135 which gives rise to the nonplanar path of motion of the eyelet 89 as illustrated in FIG. 4. Since the radial dimension of the eyelet 89 from the universal pivotal axis defined by the holding member 71 is constant, the eyelet 89 will move in a path which is within a spherical surface, but the path in such spherical surface will be nonplanar. The specific path of the eyelet 89 may be varied by selection of the specific dimension of the takeup lever arms 51 and 87, by offsetting the universal pivotal connection 71, by changing the angle A, thereby offsetting the eyelet 89 to one side of the lengthwise centerline B of the lever arm 87 as illustrated in FIG. 2.

The disposition of the block 65 about the rotating driver 46 for the takeup lever orients the path of takeup eyelet 89 with respect to the thread guiding means 97 and 98 directing the thread to and from the takeup. With the cylindrical extremity 73 of the holding member 71 disposed horizontally and on the right-hand hand side of the rotary actuator 46 as viewed in FIG. 1, the path of the takeup eyelet 89 with respect to the thread guides provides a control of the needle thread as illustrated in the graph shown in FIG. 5. In FIG. 5 in addition to the curve marked "takeup," which illustrates the manipulation of the needle thread by the takeup of this invention, a curve marked needle and loop taker demand" is shown illustrating the minimum amounts of thread required by the stitch forming instrumentalities throughout a stitch forming cycle. Also indicated on FIG. 5 are the positions along the curves corresponding to the various figures of the drawings. Thus, FIG. 8 illustrates the point in the cycle at which the takeup arm has paid out thread to the greatest degree, FIG. 9 illustrates the point in the cycle at which the takeup has drawn up the takeup curve becomes substantially horizontal for a portion of the armshaft rotation. The dwell corresponds in the stitch forming cycle to the position in which the needle is providing a loop of thread for seizure by the loop taker, and as indicated in FIG. 5 the dwell provides a takeup curve which matches very closely the actual needle and loop taker demand at this critical time in the stitch forming cycle.

The takeup mechanism of this invention, therefore, provides for manipulation of the needle thread of lockstitch sewing machine in a manner very closely matching the actual demand imposed by the stitch forming instrumentalities. In operation the takeup of this invention exhibits the attribute of a rotary tension device particularly from the standpoint of inducing a minimum of vibration. Therefore, the takeup of this invention is highly desirable where high sewing speeds are required. The takeup of this invention is also advantageous in that the influence of the needle thread may be varied by a number of possible adjustments so that the influence on the thread may be tailored to suit a wide variety of different demands.

lclaim:

1. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising:

a. a lever formed with a thread eyelet;

b. means supporting said lever for movement relative to said frame; and

c. driving means operatively connected to said lever for moving said thread eyelet in a predetennined nonplanar closed loop path. 1

2. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising:

a. input means including an arm supported by said frame;

and

b. thread controlling means operatively carried and driven by said arm and supporting a thread eyelet, the movement of said thread controlling means generating a noncircular cone in space.

3. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising:

a. input means including a cone generating element having a universal pivotal connection at one point with respect to said frame and being shifted in a circular path of motion at another point such that the movement of the imaginary line joining said points generates a circular cone in space; and

b. thread controlling means operatively carried on said cone generating element and formed with a thread eyelet, said thread eyelet being offset from said imaginary line.

4. In a lockstitch sewing machine having stitch forming mechanism including a thread carrying endwise movable needle and a circularly movable loop taker cooperating therewith in the formation of stitches, a needle thread takeup mechanism comprising input means including an element the movement of which generates a cone in space, means associated with and driven by said cone generating element having a thread eyelet offset from said cone generated in space so as to move in a closed nonplanar path providing displacement characteristics suitable for needle thread takeup action, and

thread guiding means carried by said frame and directing thread to and from said thread eyelet to provide takeup action on said needle thread such as to satisfy the thread requirements of said lockstitch forming loop taker.

5. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising a bellcrank lever including a pair of arms and having a universal pivotal connection with said frame at a point between said pair of arms, rotary drive means in said frame operatively engaging one of said pair of bellcrank arms, and a thread takeup eyelet formed in the other of said bellcrank arms.

6. A needle thread takeup as set forth in claim 5 wherein said pair of arms of said bellcrank are inclined relative to one another at an angle of approximately drical mounting stud.

8. A needle thread takeup as set forth in claim 7 in which the means for journaling said cylindrical mounting stud in said sewing machine frame supports said cylindrical mounting stud substantially perpendicular to the axis of the said rotary drive means. 

1. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising: a. a lever formed with a thread eyelet; b. means supporting said lever for movement relative to said frame; and c. driving means operatively connected to said lever for moving said thread eyelet in a predetermined nonplanar closed loop path.
 2. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising: a. input means including an arm supported by said frame; and b. thread controlling means operatively carried and driven by said arm and supporting a thread eyelet, the movement of said thread controlling means generating a noncircular cone in space.
 3. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising: a. input means including a cone generating element having a universal pivotal connection at one point with respect to said frame and being shifted in a circular path of motion at another point such that the movement of the imaginary line joining said points generates a circular cone in space; and b. thread controlling means operatively carried on said cone generating element and formed with a thread eyelet, said thread eyelet being offset from said imaginary line.
 4. In a lockstitch sewing machine having stitch forming mechanism including a thread carrying endwise movable needle and a circularly movable loop taker cooperating therewith in the formation of stitches, a needle thread takeup mechanism comprising input means including an element the movement of which generates a cone in space, means associated with and driven by said cone generatIng element having a thread eyelet offset from said cone generated in space so as to move in a closed nonplanar path providing displacement characteristics suitable for needle thread takeup action, and thread guiding means carried by said frame and directing thread to and from said thread eyelet to provide takeup action on said needle thread such as to satisfy the thread requirements of said lockstitch forming loop taker.
 5. A needle thread takeup for a sewing machine having a frame, said needle thread takeup comprising a bellcrank lever including a pair of arms and having a universal pivotal connection with said frame at a point between said pair of arms, rotary drive means in said frame operatively engaging one of said pair of bellcrank arms, and a thread takeup eyelet formed in the other of said bellcrank arms.
 6. A needle thread takeup as set forth in claim 5 wherein said pair of arms of said bellcrank are inclined relative to one another at an angle of approximately 135*.
 7. A needle thread takeup as set forth in claim 5 in which said universal pivotal connection comprises a clevis with bifurcated arms and including a cylindrical mounting stud extending parallel to said bifurcated arms, means for journaling said cylindrical mounting stud in said sewing machine frame, and a pivot pin journaled in said bellcrank lever and carried between said bifurcated arms substantially perpendicular to said cylindrical mounting stud.
 8. A needle thread takeup as set forth in claim 7 in which the means for journaling said cylindrical mounting stud in said sewing machine frame supports said cylindrical mounting stud substantially perpendicular to the axis of the said rotary drive means. 